This invention relates to a combustion chamber configuration and valve operating arrangement for a multi-valve engine.
It has been recognized that the performance of an internal combustion engine can be significantly improved by increasing the number of valves serving each of the combustion chambers. By using a plurality of smaller diameter valves rather than individual large diameter valves, it is possible to increase the total effective valve flow area without a significant increase in the weight of the reciprocating masses. As a result, multiple valve engines are receiving considerable interest and application for a wide variety of purposes, such as powering motor vehicles.
However, as the number of valves per combustion chamber increases, the complexity of the engine also increases. In addition, the added port areas necessary to serve the multiple valves tends to complicate the ability to provide a rigid cylinder head arrangement that can withstand the loadings.
It is, therefore, a principal object of this invention to provide an improved cylinder head arrangement for an internal combustion engine embodying a plurality of valves and wherein the cylinder head is formed with an integral reinforcing construction.
It is a further object of this invention to provide an improved arrangement for the cylinder head of an internal combustion engine having multiple valves wherein the cylinder head is reinforced by at least one bridging member that extends transversely across the cylinder head in proximity to the combustion chamber.
Although the use of such a bridging member or bridging members for reinforcing the cylinder head is particularly advantageous so as to provide a strong and yet lightweight construction, the use of bridging members by themselves can further complicate the overall configuration of the cylinder head and the formation of it. It is, therefore, a still further object of this invention to provide an improved cylinder head arrangement embodying a reinforcing bridging member that serves purposes in addition to merely reinforcing the cylinder head.
Where multiple intake valves are utilized in conjunction with internal combustion engines, it has been generally the practice to dispose all of the intake valves on one side of the engine and all of the exhaust valves on the other side of the engine. This is generally done so as to simplify the porting for the engine and so that the ports for the intake and exhaust gases need not cross over each other. However, where the intake and exhaust valves are so disposed on opposite sides of the cylinder head, this has generally necessitated the use of separate camshafts for operating the intake and exhaust valves, respectively. Although the use of separate camshafts has certain advantages, it further complicates the engine. Not only does this tend to raise the overall height of the engine due to the positioning of the camshafts, but it also significantly complicates the timing arrangement for driving all of the camshaft from the crankshaft of the engine. Although the use of a single overhead camshaft for operating all of the valves is possible, the previously proposed arrangements of this type have given rise to certain other problems. For example, the placement of such added components as spark plugs and the like become a significant problem in connection with the use of single overhead camshafts for multiple valve engines.
It is, therefore, a still further object of this invention to provide an improved valve actuating arrangement for multiple valve engine that employs only a single camshaft.
It is a further object of this invention to provide a multiple valve engine in which all valves are operated by a single camshaft and wherein the camshaft is so located that it will not interfere with or compromise the placement of other components of the engine such as the spark plugs.
In addition to the problems of component placement when all of the multiple valves of an engine are operated by a single camshaft, there also is a considerable problem in connection with adequate support for the camshaft. That is, where multiple valves are operated by a single camshaft, the operating loads exerted on the camshaft can be quite high. It is, of course, extremely important to support the camshaft in such a way that it will not flex and the valve operation will not be adversely affected.
It is, therefore, a still further object of this invention to provide an improved arrangement for journaling the camshaft of a multiple valve internal combustion engine.
It is a further object of this invention to provide a multiple valve, single camshaft internal combustion engine having an improved arrangement for journaling the single camshaft.
Where multiple valves are operated for an engine from a single camshaft, it is generally the practice to employ some form of rocker arm arrangement for operating the valves from the camshaft so that the valves can be located in the combustion chamber at optimum positions and may reciprocate along the desired axes. However, where rocker arms are employed, it is also necessary to provide an arrangement for pivotally journaling the rocker arms. Although individual rocker arm supports have been proposed, these supports have a tendency of permitting the rocker arm to move transversely or rotate about an axis perpendicular to their normal pivotal axis and can adversely affect high speed performance. Therefore, it is desirable to mount the rocker arms for their pivotal movement on a rocker arm shaft which shaft will tend to maintain the movement of the rocker arm in its desired path. However, the use of the rocker arm shafts can give rise to other problems, particularly in the placement of other components of the engine.
It is, therefore, a still further object of this invention to provide an improved arrangement for supporting the rocker arms of an internal combustion engine.
It is a yet further object of this invention to provide an improved rocker arm shaft arrangement for an internal combustion engine wherein the rocker arm shafts are formed in such a way as to not interfere with access to other components of the engine.
In connection with the use of multiple valves, it is a desirable practice to employ three intake valves for each cylinder of the engine. In order to facilitate operation of the valves and their placement, it has been the practice to place two of these valves, the outermost valves, so they reciprocate about parallel acute axes to a plane containing the cylinder bore axis. The third, middle valve, is disposed outwardly toward the periphery of the cylinder bore from this plane and also reciprocates about an axis that is at an acute angle to the plane but which angle is less than the aforenoted angle. Although this arrangement is particularly useful, the placement of the valve heads previously proposed has been such as to require the formation of a fairly deep recess in the peripheral edge of the piston so as to provide clearance. This can present certain difficulties.
It is, therefore, a still further object of this invention to provide an improved valve placement valve arrangement for a multiple valve engine wherein the volume of clearance areas formed in the peripheral edges of the head of the piston can be minimized.